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[AMPS] Tuners

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Subject: [AMPS] Tuners
From: (Jim Reid)
Date: Fri, 13 Mar 1998 14:11:50 -1000
At 05:47 PM 3/13/98 EST, km1h @ wrote:

>That review should have convinced any one that the MFJ was the worst
>choice for the lower bands. The efficiency of the MFJ has NOT changed
>with their much ballyhoo'ed air inductor. The LC values have not
>changed...they just do not catch on fire as much. 

MFJ  3kW tuner:  had an early one,  well 5 years ago.  Inductor wire melted
into the nylon(?) inductor core one evening on 160 meters!  Much odd odor
and smoke.  Of course the 87A was pumping out the power.  Antenna
was a full size 160 meter dipole,  but low.  Replaced the L with the
new MFJ air core inductor;  still was not happy.

Now use an XMatch by Paul Shrader, N4XM;  on any of my coax fed
antennas,  it and the 87A get along just fine.  For my very long wire
balanced antennas,  1200 foot long,  center fed doublet,  which
works fine on 160 (using the XMatch and the big Amidon 4:1 balun)
but for  80  and on,  I use a modified EFJohnson kW
Matchbox.   Modified per LB's info (W4RNL)  at his web site about
balanced antenna tuners.  Have added a big variable C in the
primary circuit to tune out the primary reactance and added
taps and a switch to select the primary input link,  L;  now the
secondary coil and two big capacitors tune up the 87A into
just about any reactance those loooong wires can present
80 thru 10.  The Matchbox,  however,  has not enough
inductor on board to tune up on 160,  no matter what!
But is a lot of fun to use!

73,  Jim,  KH7M

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